Lifier lug on blade of movable contact



June 1956 E. BARTLETT ET AL 2,751,447

LIFTER LUG ON BLADE OF MOVABLE CONTACT Filed Oct. 15, 1955 Q/vwMo/w ioowmww. Z3. 93M @Xwm @YL. @X/VUWL Mug 3, 5%.4 X2 MTL Z LHFKER LUG N BLADE OF MQVABLE CONTACT Lawrence E. Bartiett, Oliver M. Olivier, and Harry 3'- Schurnacirer, iiittshurgh, P3,, assignors tn Allis-filialrners Manufacturing Company, Miiwaukee, Wis.

Application October 15, 1953, Seriai No. 336,342

4 Claims. (Cl. 209-44) This invention relates to electrical switches, and in particular to an improvement in rotary contact assemblies that bridge stationary contact blades of dial type switches.

It has been suggested that the rotary contact of certain types of dial switches may coact with cam means or other auxiliary elements added to the switch mechanism during position transition. Those suggested arrangements for aiding movement of the rotary contact in the switching operation involve the disadvantage of adding elements to the switch mechanism and increasing the cost and complication of the switch. Further, those previously suggested devices while particularly suitable for embodiment in switches having flexible or resilient contact elements or in switches in which the rotary contact engages only a single stationary contact blade, are not suitable for adaption to dial switches having a rotary contact that bridges adjacent stationary contact blades nor where a pair of contacts simultaneously bridge adjacent blades to provide parallel current flow between the blades.

It is therefore an object of this invention to provide an improved dial type switch in which the movement of the rotary assembly across stationary blades is made easier.

Another object of this invention is to ease the transitional movement of the rotary contact assembly of a dial switch without increasing the cost of the assembly and without adding additional parts to the switch mechanism.

Still another object of this invention is to provide in a switch in which there are stationary blades bridged on their opposite contact surfaces by a pair of rotating bridging members, means for reducing the force required to effect a transition of the bridging members from one position to another, without adding parts to the switch and retaining the wiping and cleaning action that results from rubbing the movable contacts across the stationary contacts during transition.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawing in which:

Fig. l is a plan view of a multiple position dial switch illustrating an embodiment of this invention;

Fig. 2 is an enlarged partial view of the switch shown in Fig. 1;

Fig. 3 is a sectional view of the switch of Fig. 2 taken along line III-III of Fig. 2;

Fig. 4 is a sectional view taken along line IV-IV of Fig. 2;

Fig. 5 is an enlarged plan view of part of the switch shown in Fig. l, but with the rotary assembly illustrated as being moved part Way through its transition from one bridging position to the next; and

Fig. 6 is a sectional view taken along line VI-VI of Fig. 5.

The switch illustrated has an insulating panel 11 and a plurality of stationary contacts 12 of suitable conductive metal which are uniformly spaced on a circle and fastened to the panel as by bolt 13 (Fig. 3) threaded'into the contact. Each stationary contact has a blade disposed to extend parallel to the surface of the panel, and the blades are disposed that all have a common median plane parallel to the surface of the panel.

For the switch illustrated, conductive means is provided to bridge adjacent of the stationary blades. The bridging positions are the only switch positions as current .is conducted from one blade to the next through the bridging members. Preferably, the bridging conductive means is comprised of two members 16 and 17. The circumferential length of each of these bridging members on the circle of the stationary blades .is greater than the spacing between adjacent blades. Bridging member 16 is disposed to engage the upper surfaces of the blades; whereas bridging member 17 is disposed to engage the lower surfaces of the blades. With these two bridging members embodied in the rotary assembly, current from one blade to the adjacent blade passes in parallel paths through the two bridging members causing electromagnetic forces that aid in holding the bridging members in firm contact with the blades. Whereas, if only a single bridging contact were utilized this force would not be created and there would exist the possibility of the contacts separating when subjected to large currents. The conductive bridging members are preferably made of rigid, nonresilient material as they must carry relatively large currents which would heat resilient members to temperatures that would affect the material and change the characteristics of the switch.

A suitable means is provided for holding the two conductive bridging members superposed on the opposite sides of the median plane of the blades so that those members bridge opposite contact surfaces and for moving those members as a unit with respect to the blades. Further, each bridging member is preferably supported at only three points, two points being on adjacent blades and the third point being on the means for holding and moving the bridging members. The preferred embodiment of this holding and moving means illustrated includes shaft 18 disposed with its longitudinal axis at the center of the circle on which the blades are arranged and a driving arm 19 extending laterally from the shaft to which it is attached by a suitable fastening means. A tapered pin 21 and a clamping bolt 22 coacting with the split end of the driving arm are shown as a fastening means.

The driving arm is provided with driving surfaces dis posed to abut driven surfaces carried by the bridging members constituting means connecting the bridging members to the driving arm and shaft, whereby rotation of the shaft effects movement of the bridging members with respect to the blades. This connecting means is illustrated as comprising bolt 23 extending through each of the bridging members and through the driving arm which preferably is disposed between those bridging members. While this bolt may be carried by either the bridging members or the arm, in the illustrated embodiment it'is considered to be carried by the arm as that is the driving means, and the outer surface of the bolt defines the driving surface. The surfaces defining the holes in the bridging members, through which the bolt extends, define the driven surfaces abutted by the bolt surface when the shaft is turned in either direction.

Any suitable fasteningand biasing means may be pro vided for holding the driving and driven surfaces in position that they will engage and coact. This is shown as spring 24 between nut 25 on bolt 23 and washer 26 car-' ried in the outer surface of bridging member 16 on the one hand and the shoulder formed by the head of bolt 23 abutting washerli carried in the outer surface of bridging member 1*? on the other hand. Flexibility of movement of the bridging members is provided by forming curved depressions in the outer surfaces of the bridging members around the bolt receiving holes and providing the semispherical washers 26 and 27 to fit in those depressions to constitute a spherical bearing or ball joint. This is shown in Fig. 3.

The three point support of the bridging members referred to above involve, in this illustrated embodiment, embossing three protuberances on each of the bridging members. These protuberances are triangularly spaced. The two thereof most distant from the axis of the shaft are disposed on the circle of the stationary blades and are circumferentitally spaced apart a distance greater than the spacing between adjacent blades. These two protuberances constitute contact buttons 31 and 32. The third protuberance 33 is disposed intermediate the blades and the axis of the shaft and rests on a surface of the driving arm. Preferably all three protuberances extend from the same surface of the bridging member.

In addition to the driving connection between the bridging members and the driving arm mentioned above, means is provided to prevent the bridging members from rotating above the driving bolt as they are moved by the shaft of the switch. For this purpose pins 36 and 37 are carried by the driving arm at positions spaced from the bolt. The opposite ends of each of these pins extend into holes in the bridging members. The middle portion of each of these pins is of a greater diameter than either the ends thereof or the holes in the bridging members, whereby the pins are prevented from falling out of their position between the bridging members.

In constructing the switch, it is important to keep the size of that switch as small as possible to reduce the cost of the switch and to decrease the cost of the apparatus of which the switch is a component, such as the transformer casing in which the switch is embodied. The blades should be as close as possible to each other to reduce the size of the switch. A factor affecting that spacing is the potential that may be at the various blades and the electrical stress between the blades. But it is also desirable to make the switch so that movement of the rotary contacts is not too difficult, as by tapering the opposite edges of the blades to a knife edge. However, the more pointed the edges of the blades are the greater will be the electrical stress at those edges and the greater will be the spacing required between the blades. In accordance with this invention the spacing of the blades may be at a minimum as the edges of the blades may be cut to produce the least concentration of electrical stress. As is best shown in Figs. 4 and 6 those edges are quite blunt and the blades are disposed on the smallest circle possible. Just the portions of those edges near the upper and lower contact surfaces are curved.

Then in accordance with this invention to reduce the force required to move the rotary contact assembly across the blades a fourth protuberance or lug 41 is formed on each bridging member and is disposed that it coacts with the blades when the bridging members are moved. All four protuberances may be formed at one time and all may extend from the same surface of a bridging member. Lug 41 is disposed midway between the two contact buttons and is spaced from the switch shaft a distance equal to at least some portion of the blades, the lug is shown on the same are as are the contact buttons. The lug preferably extends from the bridging member surface for a distance slightly greater than that of the contact buttons. That spacing and positioning of the lifter lug may be defined with respect to the axis of the shaft or with respect to the other contact elements. For example, with regard to that axis, the angular spacing of leading edge 42 of the lug from the trailing edge 4-3 thereof is less than the angular spacing between adjacent edges of two adjacent blades. And the angular spacing between either the trailing or leading edge and the contact button closest thereto is less than the angular spacing between the opposite cireumferentially spaced edges of a blade. Considering the spacing and positioning of the lug with regard to the other contact elements the circumferential length of the lug is less than the distance between adjacent blades so that the lug does not contact a blade when the rotary assembly is in a bridging position and the distance between the leading edge or the trailing edge of the lug and the crown of the nearest contact button is less than the circumferential width of the blades.

When this switch is in a bridging position the contact buttons on the adjacent faces of the bridging members are firmly pressed on opposite contact surfaces of adjacent blades, and the third protuberances on the faces of the bridging members are firmly pressed on opposite surfaces of the driving arm. In this position the lifter lug is between the adjacent blades and does not interfere with the firm and proper contact at the support points.

As the transition from one switch position to another is started, the rotary contact assembly is moved until the leading edge of the lifter lug contacts the slightly tapered end edge portion of a blade. Since the edge of the lifter lug is slightly tapered and the lug extends from the face of the bridging member a slight distance beyond the contact buttons, the operator in turning the switch shaft will detect a slight resistance to continued movement of that rotary assembly, which is desired. This slight resistance results from the moderate lifting of the two bridging members as the lifter lugs engage the contact surfaces of the blade. The space between the edge of the edge of the lug and the button closest thereto is such that when a lug has engaged a blade contact surface and the midpoint of the bridging member is disposed near the edge of the blade, the contact buttons are suspended just beyond the opposite edge of the same blade. Continued rotation of the contact assembly results in the plateau of each lifting lug firmly rubbing the contact surface of a blade. This wiping action is accomplished without resulting wear on the contact buttons. In the continued transitional movement rotary assembly is rotated until the lifter lug leaves the blade, whereby the two contact buttons are lowered onto adjacent blades again giving feel to the switch action. By the time that the operator responds to this feel, the bridging members will be in proper position with the lifter lug midway between adjacent blades.

Although but a single embodiment of this invention has been illustrated and described, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the intended claims. Features disclosed but not claimed herein are claimed in a copending application Serial No. 280,711 of Joseph B. Hodtum, filed April 5, 1952, now Patent No. 2,686,236, issued August 10, 1954.

It is claimed and desired to secure by Letters Patent:

l. A switch comprising a panel, a plurality of stationary blades affixed to said panel and uniformly spaced on an arc and a moving contact assembly including a rigid conductive member and means for moving said conductive member with respect to said blades, the face of said member having two contact buttons and a lug disposed between said buttons, said buttons spaced apart on said member to simultaneously make contact with adjacent of said blades and said member providing a direct path for current between said buttons, said lug being formed and disposed to contact and wipe said blades over the entire surface of said blades contacted by said contact buttons upon movement of said member.

2. A switch comprising a panel, a plurality of stationary blades afirxed to said panel and uniformly spaced on an arc and a moving contact assembly including a rigid conductive member and means for moving said conductive member with respect to said blades, the face or said'rnernber having two contact buttons and a lug disposed between said buttons, said buttons spaced apart on said member to simultaneously contact adjacent of said blades and said member providing a direct path for current between said blltiOi'm, said lug extending from said face a distance greater than the extension of said contact buttons to lift said contact buttons from said blades upon movement of said member and with the circumferential length between said lug and each of said adjacent buttons being less than the circumferential length of each of said blades so that said lug contacts said blades before said buttons leave said blades upon movement of said member, said lug being formed and disposed to contact and wipe said blades over the entire surface of said blades contacted by said contact buttons upon movement of said member.

3. A switch comprising a panel, a plurality of stationary blades afiixed to said panel and uniformly spaced on an arc and a moving contact assembly including a rigid conductive member and means for moving said conductive member with respect to said blades, the face of said member having two contact buttons and a lug disposed between said two contact buttons, said buttons spaced apart to simultaneously contact adjacent of said blades and said member providing current path directly between said buttons, said lug extending from said face a distance greater than the extension of said contact buttons to lift said contact buttons from said blades upon movement of said member and having a circumferential length less than the circumferential length between adjacent blades so that said lug is free of said blades when said blades are bridged by said contact buttons, said lug being formed and disposed to contact and wipe said blades over the entire surface of said blades contacted by said contact buttons upon movement of said member.

4. A switch comprising a panel, a plurality of stationary blades afiixed to said panel and uniformly spaced on an arc and a moving contact assembly including a rigid conductive member inving two contact buttons disposed on said are and a lug between said two contact buttons and means for moving said conductive membet with respect to said blades with said buttons moving along said are, said buttons spaced apart on said member to simultaneously make point contact with adjacent of said blades and said member providing a current path directly between said buttons, the circumferential length between said lug and an adjacent said button being less than the circumferential length of each of said blades so that said lug contacts said blades before said buttons leave said blades upon rotation of said member and the circumferential length of said lug being less than the circumferential length between adjacent blades so that said lug is free of said blades when said blades are bridged by said contact buttons, said lug extending from said face a distance greater than the extension of said buttons to lift said contact buttons from said blades upon movement of said member and being formed and disposed on said are to contact and wipe said blades over the entire surface of said blades contacted by said contact buttons upon movement of said member.

References Cited in the file of this patent UNITED STATES PATENTS 1,626,463 Harrington Apr. 26, 1927 2,291,249 Nielsen July 28, 1942 2,577,225 Barry Dec. 4, 1951 FOREIGN PATENTS 394,532 Great Britain June 29, 1933 

